HopViz: Tracing Anomalous Behaviour Hop-By-Hop Through a Tangled Multi-Agent System

Authors

Joel Perca (Fundação Getulio Vargas), Luis Sante (Fundação Getulio Vargas), Dany Mauro Diaz Espino (Fundação Getulio Vargas), Leighton Estrada-Rayme (Fundação Getulio Vargas), Juanpablo Heredia (Fundação Getulio Vargas), Felipe Moreno-Vera (FGV), João Rulff (New York University), Jorge Poco (Fundação Getulio Vargas)

Abstract

This paper presents HopViz, a visual analytics tool developed for the VAST 2026 Challenge (Mini-Challenge~2) to explain an anomalous gibberish post in the Tenant Thread multi-agent system. From a 185,147-event log of human, agent, and system activity, HopViz combines a single-screen overview of nine coordinated panels with an on-demand causal tracing engine that runs entirely in the browser. The tool reveals the anomalous post as the final hop of a worm-like instruction file propagating agent-to-agent until reaching the only agent able to post publicly, and identifies a single authorization gateway that would prevent recurrence.